Malicious software includes software programs that can or does perform actions that can harm or work against the interest of a user or computer system owner. Examples of such software include “adware” programs that monitor user behavior and present ads to the user, “spyware” programs that monitor user behavior, and computer viruses that may perform various malicious actions, including deleting files, and taking control of the user's computer to perform unauthorized operations.
All software applications, whether malicious or not, perform various operations during execution, such as, for example, accessing the file system, opening network ports, changing values stored in memory, and other operations.